Vehicle bumper installation

ABSTRACT

An energy dissipating bumper installation for vehicles includes a transversely extending bumper bar mounted to the vehicle frame at transversely spaced locations on the cross member thereof by energy dissipating bumper mounted assemblies, each assembly including a generally elliptically shaped spring unit attached at opposite sides thereof along its minor axis to the cross member and to the bumper and having attached across its major axis an irreversible energy dissipating tension strut adapted to provide controlled resistance to flattening tendencies of the spring unit under impact forces applied to the bumper bar.

United States Patent Zimmerle [451 May 16, 1972 [54] VEHICLE BUMPERINSTALLATION [72] Inventor: Wilbur J. Zimmerle, Bellbrook, Ohio [73]Assignee: General Motors Corporation, Detroit,

Mich.

[22] Filed: Apr. 3, 1970 [21] Appl. No.: 25,360

[52] US. Cl. ..293/84, 293/91, 293/D1G. 3,

267/142, 188/1 C [51] Int. Cl. ..B60r 19/08 [58] Field of Search..293/84, 85, 87, 91, 92, 93, 293/94; 267/8, 42; 188/1 C [56] ReferencesCited UNITED STATES PATENTS 1,468,868 9/1923 Reichstetter et a1 ..293/921,697,204 l/1929 Nomicos ...293/85 3,026,972 3/1962 l-lendry et al..188/1 C 759,507 7/1903 Ericsonetal.....

I FOREIGN PATENTS OR APPLICATIONS 6/1928 France ..293/85 452,217 5/1913France ..267/8 522,448 8/1928 Germany ..293/91 Primary ExaminerArthur LLa Point Assistant Examiner-Robert Saifer AltorneyD. L. Ellis and W. E.Finken [57] ABSTRACT An energy dissipating bumper installation forvehicles includes a transversely extending bumper bar mounted to thevehicle frame at transversely spaced locations on the cross memberthereof by energy dissipating bumper mounted assemblies, each assemblyincluding a generally elliptically shaped spring unit attached atopposite sides thereof along its minor axis to the cross member and tothe bumper and having attached across its major axis an irreversibleenergy dissipating tension strut adapted to provide controlledresistance to flattening tendencies of the spring unit under impactforces applied to the bumper bar.

3 Claims, 5 Drawing Figures VEHICLE BUMPER INSTALLATION This inventionrelates to vehicle bumpers and more particularly to an energydissipating collision bumper installation for automotive vehicles.

This invention has as its primary feature the provision of an energydissipating vehicle bumper installation including a collision bumper barextending transversely of the vehicle and mounted to an end cross memberof the frame thereof by two or more bumper mounting units comprisingelliptical spring members adapted to undergo elastic strain under impactforces applied to the bumper bar, such spring units being furtherprovided across their major axes with tension struts operative topresent a controlled resistance to and an irreversible dissipation ofthe energy of the impact forces tending to flatten the ellipticalspring.

The energy dissipating means may take the form of either a viscousdamper type tension strut, as for example a piston and sleeve unitutilizing a hydraulic medium to resist telescopic ex tension thereofunder tension forces, or alternatively may take the form of a telescopicsleeve and rod unit provided with extrusion or metalupsettingconformation to achieve irreversible energy dissipation. In the case ofthe latter, the sleeve and rod unit may be employed to prestress theelliptical spring from a preformed unstressed elliptical shape to adeeper elliptical shape across its minor axis whereby largerdisplacement or flattening is available to the spring units and thebumper bar under collision forces.

More specifically, the elliptically shaped spring unit is adapted forattachment at opposite sides to the frame cross member and bumper bar onflat faces thereof, the spring unit having such a specific shapeincluding front and back portions engaged on these flat faces andgenerally semicircular end portions that successive portions of thefront and back portions are engageable with the frame and bumper facesto flatten thereover while the end portions remain semicircular butofsuccessively smaller diameter.

In the preferred embodiment, the elliptical spring unit comprisesseveral elliptical layers made into a unit to insure elastic actionthroughout its excursion while exhibiting high deflection rate.

These and other features and advantages of the invention will be readilyapparent from the following specificationand from the drawings wherein:

FIG. 1 is a partially phantom fragmentary perspective view of anautomotive vehicle having a vehicle bumper installation according tothis invention;

FIG. 2 is a horizontal sectional view taken generally along the planeindicated by lines 2--2 ofFIG. 1;

FIG. 3 is an enlarged view of a portion of FIG. 2 showing in broken andsolid lines respectively normal and prestressed conditions of theelliptical spring unit;

FIG. 4 is an enlarged sectional view taken generally along the planeindicated by lines 4-4 of FIG. 3; and

FIG. 5 is a view similar to FIG. 3 showing a modification of theelliptical spring unit.

Referring now particularly to FIG. 1 of the drawings, there isillustrated therein in phantom the front end portion of an automotivevehicle designated generally as including a chassis frame conventionallycomprised of longitudinally extending side rails such as indicated at12, adapted to be joined at the forward extremities thereof by a frontcross member. It is to be understood that while the drawings illustratea separate chassis-frame, the invention is equally well applied tovehicles employing unibody construction wherein the rigidifying frameand body sheet metal components are fabricated integrally with eachother.

A front collision bumper installation, according to this invention,includes a specially adapted front frame cross member 14 of generallyU-shape in plan view and including rearwardly extending legs 16 weldedor otherwise attached to the forward extremities of the front side rails12. A generally oval-shaped in elevation bumper or collision bar 18including upper and lower transverse portions 20 and 22 defines, asillustrated, a grille opening therebetween for exposing a vehicle grillestructure indicated at 24 mounted to the front body portion of vehicle10 rearwardly of the forward extremities of the bumper l8. Bumper 18 isdesigned in conjunction with the two front fenders of the vehicle, thehood thereof, and the lower splash shield 25 below the grille suitablyto pennit telescoping of bumper 18 into the front end portion of thebody under collision forces. Such telescoping is permitted by the bumperinstallation or mounting components to be described hereinafter.Further, if desired, the bumper 18 may be fabricated of a compositeconstruction including an inner steel backbone having molded thereover ahigh density selfskinning polyurethane foam or other desired elastomeroperative to resiliently sustain minor bumps and abrasions withoutdamage.

Referring now more particularly to FIGS. 2 and 3, bumper 18 is mountedon vehicle 10 by a transversely spaced pair of elliptical spring unitsdesignated generally as 26. In a preferred form, each spring may befabricated of a single length of steel band or strip wrapped over itselfseveral times to provide several layers or laminations, with the twoends of the bar being secured together by localized welding at theterminal ends of alternatively held by fasteners as will be described.Considering that the spring unit 26 is to perform entirely elastically;i.e., without any onset of any substantial plastic strain when subjectedto collision forces up to a predetermined maximum design level, it isdesirable to provide such layers or laminations so that each layer maybend or elastically deform over substantial distance longitudinally ofvehicle 10 without such plastic strain, rather than providing a singlethick elliptical band which could perhaps sustain an equal load but withmuch less deflection without fracture or yield. The several laminationscontribute jointly to the spring rate of the entire assembly and thusprovide a high composite spring rate without undue tendency towardplastic strain. It will of course be appreciated that these objectivesmay be accomplished also with the aid of different selections ofmaterial having varying stress-strain characteristics. However, in thepreferred embodiment, the laminated construction employs SAE 1070 steelwherein the band is 0.109 inches thick and has a vertical or heightdimension in elevation of approximately 3 inches.

As seen best in FIG. 3, the spring units 26 are first fabricated into apreformed or normal unstressed condition shown in broken lines. Wheninstalled in the vehicle, however, the spring unit is prestressed to adeeper generally elliptical shape wherein the major and minor axesthereof are shorter and longer respectively than those of the unstressedcondition. This prestress is accomplished by selected adjustment withina tension strut device 28 extending across the major axis of the springunit. The tension strut, in a preferred form, comprises a rod 30 and asleeve 32 telescopically joined together, with the leftward end ofsleeve 32 having welded thereto one end of a threaded stud 34. The endof rod 30 is also threaded and nuts 36 are threaded onto rod 30 and stud34 within the spring unit. The stud and rod extend through suitableopposed apertures in the spring unit band laminations to receivesimilarly apertured reinforcements 38, and a further pair of nuts 40 arethreaded over the nut and rod into engagement with the reinforcements.

As also indicated in FIG. 4, the internal end of rod 30 is provided withan enlarged extruding head 42 having flats formed at intervalstherearound to define a generally rectangular profile presented to ashoulder 44 of the sleeve 32 defined by smaller and larger diameterportions thereof. In its initial assembled state, tension is appliedthrough strut 28 to bottom head 42 on shoulder 44 and the nuts 36 and 40are tightened to deform the spring unit from the relatively shallownormal or unstressed condition shown in broken lines to the prestressedcondition, shown in solid lines, whereupon the nuts are tightened andthe spring units are ready for installation on the vehicle 10.

As indicated best in FIGS. 1 and 2, the prestressed spring units 26 areeach mounted to the lower portion 22 of bumper 18 by four bolts 47extending through apertures in the laminated band of the spring units.The spring units bands are engaged flushly on rigid load bearing steelbackbone or other flat surfaces 46 formed on the rearward face of thebumper lower portion 22. Similarly, as indicated in FIG. 3, the springunits are mounted to flat surfaces 48 formed on the cross member 14,four bolts 49 again being employed to extend through apertures in thelaminated band.

While being described as being generally of elliptical shape, it is seenfrom the drawings that spring units 26 most specifically take asemi-elliptical form since, with the aid of bolts 47 and 49, thespringunits have front and back portions 50 and 52 which are flat, andgenerally semicircular end portions 54 and 56. This generalcharacteristic of the shape is retained during deformation of the springunits under collision forces applied to bumper 18 and providesadvantages to be described hereinafter.

With the bumper 18 so mounted at the lower end portion 22 thereof,additional installation components are provided to stabilize the bumperon the vehicle against road induced vibration and include a pair ofviscous damper units 58 each pinned at opposite ends to a bracket 60 onthe cross member 14 and a bracket 62 on the upper portion of the bumper.Thedamper units 58 are telescopic and allow for relative motion ofbumper l8.telescopically into the front body sheet metal as previouslydescribed, yet provides sufficient damping or resistance to periodic lowenergy vibration induced by road irregularities so that the bumper doesnot shake in a verticalof longitudinal displacement mode to anyobjectionable degree about its lower spring mountings.

The spring units 26 and bumper 18 are constrained to deflect ingenerally longitudinal planes of the vehicle 10 through rods64-extending between a bracket 66 centrally located on bumper 18 andthrough apertures in upper brackets 68 on cross member 14, and a similarpair of rods 70 extending between bracket 66 and similar brackets on thelower side of the cross member. Nuts are provided on the remote threadedends of all of these rods to bottom on the cross member brackets whenthe bumper 18 is located in its normal extended position shown in solidlines in FIG. 2. As indicated in broken lines, rods 64 and 70 arelaterally displaceable through the apertures in brackets 68 and 72 tothe extent dictated by the rod geometry under collision forcestelescoping bumper 18 rearwardly of the vehicle. However, itis seen thatthe pivot connections of the rods afforded at bracket 66 and by the nutson the rod ends prevent any significant amount of lateral displacementof bumper 18 as might occur under a cornering impact at either sideofthe bumper.

In the event of collision forces applied to bumper 18 forcing thelatter'rearwardly of the vehicle, the spring units 26 are caused toelastically deform from their prestressed elliptical shape shown insolid lines in FIG. 2 to any flattened elliptical shape up to a maximumdeflection condition shown in broken lines. As is seen, cross member 14is bowed in plan view rearwardly in its central portion to allow forrearward excursion of bracket 66 to this maximum deflection condition.While so deflecting, tension strut 28 is operative to provide acontrolled amount of resistance to elastic flattening of the spring unitbands and provides dissipation of the energy of the forces causing suchflattening through the action of head 42 on rod 30. When collisionforces of a predetermined magnitude sufficient to begin metal upsettingin sleeve 32 are so applied, the head extrudes progressive portions ofthe smaller diameter sleeve end as tension strut 28 is caused tolengthen or telescope under the forces causing the flattening orlengthening of the major axis dimension of the elliptical bands of thespring units. Depending upon the severity or energy of the collision onbumper 18, the elliptical springs may flatten to a small degree and thetension struts only slightly elongated or, in high energy impacts, thespring may flatten fully to the position indicated in broken lines inFIG. 2 and the tension strut elongated to a maximum length. With slightimpacts, any irreversible energy dissipation and lengthening of tensionstrut 28 serves to reduce the prestress of the spring unit allowing itto take a shape more akin to its unstressed shape, and successive suchimpacts may remove the prestress entirely. It is of course understoodthat the elliptical bands always seek at least such unstressed shapeafter more severe impacts. However, the tension strut may be reused forsubsequent energy dissipation under impacts by adjustment of nuts 36 and40 on the threaded rod and stud to again telescope the tension strutinto a tension bearing condition between the ends of the spring unit andprestressing of the latter. When sleeves 32 are fully expended, newtension struts may be installed.

As indicated in FIG. 2, the elliptical bands of the spring units tend toalways seek the generalized shape indicated thereabove; i.e., flat frontand back portions merging with semicircular end portions. During theelastic deflection of the elliptical bands, this is aided by successiveportions of the semicircular end portions engaging the flat surfaces 46and 48 of the cross member and bumper. These successively longer frontand back portions remain joined by end portions taking successivelysmaller diameter semicircular shape due to the tendency of these endportions to distribute the stresses equally therearound. It has beenfound that this effect and the combination of factors just describedwhich lead thereto result in the spring units 26 having a generallyconstant rate of deflection under a sustained load as the units undergosuccessively flattened shapes. The forces in the semicircular endportions and the deflected flat portions of the spring units do not tendtoward an infinite value in fully flattened condition as with springunits of different shape, for example, those wherein the remote ends ofthe unit take an abrupt change in curvature, rather than semicircular,in the unstressed condition. It is to be noted that whether thecollision forces applied to bumper 18 are of a relatively small'value orsufficient to fully flatten the spring units, the latter always returnthe bumper to its unstressed condition bringing the bumper back togenerally design location as shown in FIG. I. As the tension struts 28are gradually expended by repeated impacts, it is advantageous toreadjust or replace them to again prestress the spring units since it isseen that such prestress affords a large displacement excursion of theresilient bands for a given strength of material and size of bandlamination without loading the same to yield.

In FIG. 5 is illustrated a modification of spring unit 26 wherein aviscous damper tension strut 74 includes cylinder and piston portions 76and 78 attached to the spring band across its major axis. Orifices 80 inthe piston head present resistance to flattening of the spring unit inmuch the same manner as described above, with a hydraulic mediumcontained in the chambers of the cylinder.

Having thus described the invention, what is claimed is:

l. Collision bumper apparatus for vehicles comprising a col-. lisionbumper memberadapted to extend transversely across an end of a vehicle,a yieldable bumper mounting assembly including a band of resilientlydeformable material joined at its ends to define a closed figure in planview taking a predetermined generally elliptical shape in unstressedcondition including generally semicircular end portions merging withgenerally flat front and back portions, an irreversible tension strutadjustably extending across the major axis of said ellipticalband andadapted for attachment at its opposite ends thereto, the length of saidtension strut being shorter than the major axis of said elliptical band,means attaching the opposite ends of said tension strut to saidelliptical band causing the latter to be. prestressed into an ellipticalshape including generally semicircular end portions merging withgenerally flat front and back portions and having its major and minordimensions shorter and longer respectively than that of said unstressedelliptical shape, said assembly further including means on saidelliptical band located generally at the minor axis thereof attachingthe full length of said front flat portion of said band to said bumpermember, and means on said elliptical band opposite the last mentionedattaching means for attaching the full length of said back flat portionof said elliptical band to a vehicle whereby impact forces applied tosaid bumper are distributed evenly through said band semi-circular endportions.

2. Collision bumper apparatus for vehicles comprising a collision bumpermember adapted to extend transversely across an end of a vehicle, ayieldable bumper mounting assembly including a band of resilientlydeformable material joined at its ends to define a closed figure in planview taking a predetermined generally elliptical shape in unstressedcondition including generally semicircular end portions merging withgenerally flat front and back portions, a tension strut extending acrossthe major axis of said elliptical band and adapted for attachment at itsopposite ends thereto, the length of said tension strut being shorterthan the major axis of said elliptical band and said tension strutincluding irreversibly deformable means for imparting a controlledresistance to lengthening of said strut under application thereto oftension loads above a predetermined value, means adjustably attachingthe opposite ends of said tension strut to said elliptical band causingthe latter to be prestressed, by tension in said strut below saidpredetermined value, into an elliptical shape including generallysemicircular end portions merging with generally flat front and backportions and having its major and minor dimensions shorter and longerrespectively than that of said unstressed elliptical shape, saidadjustable attaching means being capable of adjustment compensating fora limited amount of deformation of said strut deformable means andreestablishing the desired prestress, in said band after receipt of animpact force, said assembly further including a flat portion on saidelliptical band located generally at the minor axis dimension thereofattaching the full length of the flat portion of said band to saidbumper member and a flat portion on said elliptical band opposite thelast mentioned attaching means for attaching the full length of the flatportion of said elliptical band to a vehicle whereby impact forcesapplied to said bumper are evenly distributed through said bandsemicircular end portions.

3. In a vehicle, collision bumper apparatus comprising, a

vehicle structural frame member extending generally transversely of thevehicle at one end thereof and providing transversely spaced generallyflat bumper mounting faces, a collision bumper member adapted to extendtransversely of said end of the vehicle in spaced relation to said framemember, said bumper member providing flat mounting faces respective toand disposed oppositely of one of said mounting faces of said framemember, and at least a pair of elastically yieldable bumper mountingassemblies each located adjacent one end of said bumper member, eachsaid assembly including a lamination unit of a plurality of resilientlydeformable bands attached together and formed to define a generallyelliptical unstressed shape in horizontal section, a tension strutextending across the major axis of said elliptical lamination unit andbeing shorter than the unstressed dimension thereof thereacross, meansattaching the opposite ends of said strut to said unit causing thelatter to take a prestressed elliptical shape having major and minoraxis dimensions shorter and longer respectively than that of saidunstressed shape, said stressed shape including opposite generallysemicircular end portions merging with generally flat front and backportions, one of said front and back portions being attached to a flatmounting face of said bumper member while the other thereof is attachedto a flat mounting face of said frame member, said elliptical band beingelastically yieldable under forces applied to said bumper toward saidframe member and while so deflecting having successive portions of saidend portions thereof engageable on said flat faces to take the flatconformation thereof while the end portions take successively smallerdiameter generally semicircular shape, said tension strut includingtelescopically related rod and sleeve members operative under tension insaid strut above a predetermined value to cause irreversible deformationtherein during lengthening thereof, and stabilizing linkage connectingsaid bumper member and said frame member to control displacementtherebetween to occur strictly in longitudinal planes of the vehicle.

1. Collision bumper apparatus for vehicles comprising a collision bumpermember adapted to extend transversely across an end of a vehicle, ayieldable bumper mounting assembly including a band of resilientlydeformable material joined at its ends to define a closed figure in planview taking a predetermined generally elliptical shape in unstressedcondition including generally semicircular end portions merging withgenerally flat front and back portions, an irreversible tension strutadjustably extending across the major axis of said elliptical band andadapted for attachment at its opposite ends thereto, the length of saidtension strut being shorter than the major axis of said elliptical band,means attaching the opposite ends of said tension strut to saidelliptical band causing the latter to be prestressed into an ellipticalshape including generally semicircular end portions merging withgenerally flat front and back portions and having its major and minordimensions shorter and longer respectively than that of said unstressedelliptical shape, said assembly further including means on saidelliptical band located generally at the minor axis thereof attachingthe full length of said front flat portion of said band to said bumpermember, and means on said elliptical band opposite the last mentionedattaching means for attaching the full length of said back flat portionof said elliptical band to a vehicle whereby impact forces applied tosaid bumper are distributed evenly through said band semi-circular endportions.
 2. Collision bumper apparatus for vehicles comprising acollision bumper member adapted to extend transversely across an end ofa vehicle, a yieldable bumper mounting assembly including a band ofresiliently deformable material joined at its ends to define a closedfigure in plan view taking a predetermined generally elliptical shape inunstressed condition including generally semicircular end portionsmerging with generally flat front and back portions, a tension strutextending across the major axis of said elliptical band and adapted forattachment at its opposite ends thereto, the length of said tensionstrut being shorter than the major axis of said elliptical band and saidtension strut including irreversibly deformable means for imparting acontrolled resistance to lengthening of said strut under applicationthereto of tension loads above a predetermined value, means adjustablyattaching the opposite ends of said tension strut to said ellipticalband causing the latter to be prestressed, by tension in said strutbelow said predetermined value, into an elliptical shape includinggenerally semicircular end portions merging with generally flat frontand back portions and having its major and minor dimensions shorter andlonger respectively than that of said unstressed elliptical shape, saidadjustable attaching means being capable of adjustment compensating fora limited amount of deformation of said strut deformable means andreestablishing the desired preStress in said band after receipt of animpact force, said assembly further including a flat portion on saidelliptical band located generally at the minor axis dimension thereofattaching the full length of the flat portion of said band to saidbumper member and a flat portion on said elliptical band opposite thelast mentioned attaching means for attaching the full length of the flatportion of said elliptical band to a vehicle whereby impact forcesapplied to said bumper are evenly distributed through said bandsemicircular end portions.
 3. In a vehicle, collision bumper apparatuscomprising, a vehicle structural frame member extending generallytransversely of the vehicle at one end thereof and providingtransversely spaced generally flat bumper mounting faces, a collisionbumper member adapted to extend transversely of said end of the vehiclein spaced relation to said frame member, said bumper member providingflat mounting faces respective to and disposed oppositely of one of saidmounting faces of said frame member, and at least a pair of elasticallyyieldable bumper mounting assemblies each located adjacent one end ofsaid bumper member, each said assembly including a lamination unit of aplurality of resiliently deformable bands attached together and formedto define a generally elliptical unstressed shape in horizontal section,a tension strut extending across the major axis of said ellipticallamination unit and being shorter than the unstressed dimension thereofthereacross, means attaching the opposite ends of said strut to saidunit causing the latter to take a prestressed elliptical shape havingmajor and minor axis dimensions shorter and longer respectively thanthat of said unstressed shape, said stressed shape including oppositegenerally semicircular end portions merging with generally flat frontand back portions, one of said front and back portions being attached toa flat mounting face of said bumper member while the other thereof isattached to a flat mounting face of said frame member, said ellipticalband being elastically yieldable under forces applied to said bumpertoward said frame member and while so deflecting having successiveportions of said end portions thereof engageable on said flat faces totake the flat conformation thereof while the end portions takesuccessively smaller diameter generally semicircular shape, said tensionstrut including telescopically related rod and sleeve members operativeunder tension in said strut above a predetermined value to causeirreversible deformation therein during lengthening thereof, andstabilizing linkage connecting said bumper member and said frame memberto control displacement therebetween to occur strictly in longitudinalplanes of the vehicle.